Until the issue is fixed, you can add a simple script that will remove the height attribute that causes the problem. Here are two examples:

With a RadWindow's ContentTemplate

            <asp:Button ID="Button1" Text="open wnd" OnClientClick="openWnd(); return false;" runat="server" />
            <telerik:RadWindow runat="server" ID="resultsWindow" Modal="true" Height="700px" Width="1100px" VisibleStatusbar="false" OnClientShow="repaintWizard">
                <ContentTemplate>
                    <telerik:RadWizard runat="server" ID="ResultsWizard" ActiveStepIndex="0" RenderedSteps="Active" DisplayProgressBar="false">
                        <WizardSteps>
                            <telerik:RadWizardStep runat="server" ID="SelectStatus" StepType="Start" TabIndex="0">
                                <telerik:RadButton runat="server" ID="StatusWizard" ToggleType="Radio">
                                    <ToggleStates>
                                        <telerik:RadButtonToggleState Text="Passed" />
                                        <telerik:RadButtonToggleState Text="Failed" />
                                    </ToggleStates>
                                </telerik:RadButton>
                            </telerik:RadWizardStep>
                        </WizardSteps>
                    </telerik:RadWizard>
                </ContentTemplate>
            </telerik:RadWindow>
            <script>
                function repaintWizard(sender, args) {
                    $telerik.$(".rwzContent", sender.get_contentElement()).height("");
                }

                function openWnd() {
                    $find("<%=resultsWindow.ClientID%>").show();
                }
            </script>

In a simple hidden div:

			<script>
				function showDiv() {
					var theDiv = $get("testDiv");
					theDiv.style.display = "";
					$telerik.$(".rwzContent", theDiv).height("");
				}

			</script>
			<asp:Button ID="Button1" Text="show div" OnClientClick="showDiv(); return false;" runat="server" />
			<div id="testDiv" style="display:none;">
				<telerik:RadWizard runat="server" ID="RadWizard1" ActiveStepIndex="0" RenderedSteps="Active" DisplayProgressBar="false">
					<WizardSteps>
						<telerik:RadWizardStep runat="server" ID="RadWizardStep1" StepType="Start" TabIndex="0">
							<telerik:RadButton runat="server" ID="RadButton1" ToggleType="Radio">
								<ToggleStates>
									<telerik:RadButtonToggleState Text="Passed" />
									<telerik:RadButtonToggleState Text="Failed" />
								</ToggleStates>
							</telerik:RadButton>
						</telerik:RadWizardStep>
					</WizardSteps>
				</telerik:RadWizard>

Steps to reproduce:
1. Created a UserControl(.ascx) for implementing wizard control
2. Created wizard control with 2 steps
3. For each step placed a TextBox with Required Field Validator
4. Also place one extra button to verify the issue, generate its event as well
5. Now generate Next, Previous and Cancel button events for Wizard control
6. Now Click on Next button to generate required field validation on text box
7. Now Click on Back or Cancel or extra button 
8. No event will be fired on single time, you have to click twice for each and every event
9. Can we get fix or solution for this, ASAP?

Please let me know if any further information is required, attaching the POC created to show the issue. 

Thanks for your help in advance!

Arvinder Singh Arora

New property that controls this behavior is added -  ClickActiveStep with default value false.